Package: cups Version: 1.3.7-7 Severity: normal I have just tried connecting a serial printer to ttyS0, with default permissions: crw-rw---- 1 root dialout 4, 64 2008-07-09 00:35 /dev/ttyS0
When I tried to add it via the web UI, the serial port wasn't listed in the Device drop-down. I turned on debug logging, and sure enough: I [09/Jul/2008:00:51:39 +0100] Started "/usr/lib/cups/daemon/cups-deviced" (pid=4656) D [09/Jul/2008:00:51:39 +0100] [cups-deviced] Added device "http"... D [09/Jul/2008:00:51:39 +0100] [cups-deviced] Added device "lpd"... D [09/Jul/2008:00:51:39 +0100] [cups-deviced] Added device "ipp"... D [09/Jul/2008:00:51:40 +0100] [cups-deviced] Added device "parallel:/dev/lp0"... D [09/Jul/2008:00:51:41 +0100] [cups-deviced] Added device "scsi"... D [09/Jul/2008:00:51:41 +0100] [cups-deviced] Added device "socket"... D [09/Jul/2008:00:51:41 +0100] [cups-deviced] Added device "beh"... D [09/Jul/2008:00:51:41 +0100] PID 4656 (/usr/lib/cups/daemon/cups-deviced) exited with no errors. I noted that cups runs as root, and sure enough, running cups-deviced as root (with arbitrary parameters) gave the same result: # /usr/lib/cups/daemon/cups-deviced 1 10 1 all DEBUG: [cups-deviced] Added device "http"... DEBUG: [cups-deviced] Added device "lpd"... DEBUG: [cups-deviced] Added device "ipp"... DEBUG: [cups-deviced] Added device "scsi"... DEBUG: [cups-deviced] Added device "socket"... DEBUG: [cups-deviced] Added device "beh"... Content-Type: application/ipp <snip> However, the same command as a normal user worked for the serial backend if not others (snip follows): DEBUG: [cups-deviced] Added device "serial:/dev/ttyS0?baud=115200"... I then tried configuring a suitable printer directly in printers.conf. When I tried printing to it, I got: E [09/Jul/2008:01:03:02 +0100] PID 4767 (/usr/lib/cups/backend/serial) stopped with status 1! E [09/Jul/2008:01:03:02 +0100] [Job 217] Unable to open device file "/dev/ttyS0": Permission denied This led me to suspect permissions, and sure enough, changing /dev/ttyS0 to 0666 worked. I didn't really understand this, as root had rw permissions anyway. I had a glance at scheduler/cups-deviced.c, and there is certainly some magic there relating to the user that it runs the backend as. Unfortunately, I don't have time to delve deeper, but see comments around line 204. I don't want /dev/ttyS0 to be world readable/writeable, but I don't see what else to do for now. NB lp is already in my dialout group, that didn't help. Anyway, this wasn't documented anywhere that I can see. I'm not sure what you think is the best way forward, but at the very least, I think this should be documented in README.Debian[1], with suitable guidance given as to possible permission settings for the serial port. Better still, it should just work. Thanks, Antony [1] Another thing - could we please have a README.Debian in /usr/share/doc/cups that at least points to /usr/share/doc/libcups2/README.Debian.gz? I had to use apt-file and grep to find it. -- System Information: Debian Release: lenny/sid APT prefers unstable APT policy: (500, 'unstable'), (500, 'testing') Architecture: amd64 (x86_64) Kernel: Linux 2.6.24-1-amd64 (SMP w/1 CPU core) Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/bash Versions of packages cups depends on: ii adduser 3.108 add and remove users and groups ii cups-common 1.3.7-7 Common UNIX Printing System(tm) - ii debconf [debconf-2.0] 1.5.22 Debian configuration management sy ii ghostscript 8.62.dfsg.1-2.1 The GPL Ghostscript PostScript/PDF ii libavahi-compat-libdn 0.6.22-3 Avahi Apple Bonjour compatibility ii libc6 2.7-10 GNU C Library: Shared libraries ii libcups2 1.3.7-7 Common UNIX Printing System(tm) - ii libcupsimage2 1.3.7-7 Common UNIX Printing System(tm) - ii libdbus-1-3 1.2.1-2 simple interprocess messaging syst ii libgnutls26 2.4.0-2 the GNU TLS library - runtime libr ii libkrb53 1.6.dfsg.4~beta1-3 MIT Kerberos runtime libraries ii libldap-2.4-2 2.4.9-1 OpenLDAP libraries ii libpam0g 0.99.7.1-6 Pluggable Authentication Modules l ii libpaper1 1.1.23+nmu1 library for handling paper charact ii libslp1 1.2.1-7.3 OpenSLP libraries ii lsb-base 3.2-12 Linux Standard Base 3.2 init scrip ii perl-modules 5.10.0-11 Core Perl modules ii procps 1:3.2.7-8 /proc file system utilities ii ssl-cert 1.0.21 simple debconf wrapper for OpenSSL ii xpdf-utils [poppler-u 3.02-1.3 Portable Document Format (PDF) sui Versions of packages cups recommends: ii avahi-utils 0.6.22-3 Avahi browsing, publishing and dis ii cups-client 1.3.7-7 Common UNIX Printing System(tm) - ii foomatic-filters 3.0.2-20080211-3.1 OpenPrinting printer support - fil ii smbclient 2:3.0.30-3 a LanManager-like simple client fo -- debconf information: cupsys/raw-print: true cupsys/backend: ipp, lpd, parallel, scsi, serial, socket, usb, snmp, dnssd -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]